# A car travels at constant speed around a circular roundabout. Explain why the car is accelerating even though its speed is not changing, and describe the direction and cause of the resultant force that produces this acceleration.

> Eduqas A-Level Physics — 1.5 Circular motion (A-Level only) · Explain · 5 marks

## Mark scheme (5 marks)

1. Velocity is a vector quantity, having both magnitude (speed) and direction
2. The direction of the car's motion is continuously changing as it goes around the roundabout
3. A change in velocity (even at constant speed) means the car is accelerating
4. The resultant force (centripetal force) acts towards the centre of the roundabout / circle
5. This resultant force is provided by friction between the car's tyres and the road surface

## Key terms

- [acceleration](https://www.gradenine.co.uk/glossary/acceleration)
- [resultant force](https://www.gradenine.co.uk/glossary/resultant-force)

## Related

- [Revision notes for Eduqas A-Level Physics](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-car-travels-at-constant-speed-3cc18ff0) · Published by Druglandscape Ltd.